Conventionally, a transmission of a vehicle is provided with a parking lock device. The parking lock device prevents a vehicle from moving unintentionally by engaging a parking gear with a lock pawl, which are arranged inside the transmission, when a shift lever is shifted to a parking range (P range).
In this type of the parking lock device, as disclosed in Patent Document 1, for example, as an actuator (motor) rotates a detent plate via a control rod, an automatic transmission control device and a park rod are simultaneously operated. By driving the actuator, when the automatic transmission control device is shifted to the P range, a conical lock cam provided at the distal end of the park rod displaces the lock pawl to a locked position, at which the lock pawl engages with the parking gear. Thereby, the parking gear engaged with the lock pawl is prevented from being rotated, so that rotation of the output shaft of the automatic transmission is also restricted. At that moment, displacement of the detent plate is determined by a detent spring with a roller to be held in the P range.